A blast furnace is supplied at its base with a large quantity of air, optionally enriched with oxygen, called a "blast". This blast is generally compressed, often to a pressure of between 3 and 6 bar, by one or more axial compressors called "blowers".
Since these compressors are not equipped with an interstage cooler, the compression then carried out is of the adiabatic type and some of the energy expended serves to heat the blast which, thus compressed, leaves the blower at a temperature of between 150.degree. and 250.degree. C.
The amount of water contained in the blast corresponds in this case to the amount of water contained in the ambient air.